Lithium Salt-Induced In Situ Polymerizations Enable Double Network Polymer Electrolytes.

Structural design is an intriguing strategy to improve the physical and electrochemical performance of polymer electrolytes (PEs) for lithium-ion batteries. However, the complex synthetic process and introduction of nonelectrolyte composition severely limit the development and practical application of PEs. Here, a facile method is reported for the fabrication of a double network polymer electrolyte (DN-PE) through combining the lithium salt-accelerated thiol-Michael addition and lithium salt-catalyzed radical polymerization. By adjusting the reaction temperature, the double network with the cross-linking structure can be in situ formed step by step at room temperature and 80 °C. Notably, using lithium salt as the accelerator and catalyst avoids the addition of extra species and the related side reactions in the electrolyte system. Compared with single network polymer electrolyte (SN-PE), DN-PE has a distinctly improved mechanical strength and a better interfacial compatibility with the electrode, which leads to a stable cycling of the symmetric Li|DN-PE|Li cell over 1000 h at a current density of 0.05 mA cm -2 . In addition, the Li|DN-PE|LiFePO 4 cell shows a high discharge specific capacity of 150.3 mAh g -1 at 0.1 C and coulomb efficiency of 99%.